CutPlane is a Photoshop plug-in filter. It looks at each pixel in the selection and manipulates the bits in it.
When you choose the CutPlane filter, you get a dialog box which invites you to set certain check boxes corresponding to the bits in a target byte. Plane 7 corresponds to the most significant (left-most) bit in the byte, plane 0 to the least significant.
So if you set planes 7, 5, & 1, the filter creates a byte 10100001. This byte is compared with the components of each pixel (three components for RGB, one for greyscale). Bits which are on in the target byte are set to zero in the component byte. So, with the target byte given, the input bytes 11111111, 01011111, 00101111 are output as 01011110, 01011110, 00001110.
If the Normalise checkbox is checked, and the leftmost bit of the target byte is zero, the component result bytes are shifted left by the amount which would make the leftmost bit of the target byte 1. So if the target byte is 00011110, each result component byte is shifted left 3 times.
Copy the filter to the Photoshop Plug-ins folder to use. I’ve supplied PowerPC (PPC) and 680x0 (68K) versions.
